Ignition apparatus for internal combustion engine

Abstract

An ignition apparatus for an internal combustion engine includes means for generating signals indicating when the crankshaft and camshaft of the engine have respectively reached predetermined angular positions, a command circuit for initiating and terminating ignition operation in response to these position signals, and means for establishing a first operating condition, following each camshaft position pulse, in which the ignition operation is enabled and a second operating condition, following a subsequent crankshaft position pulse, in which ignition operation is inhibited, to thereby eliminate redundant ignition operation and the attendant power loss and heat generation. The apparatus also includes a timer circuit which act to enable resetting to the second operating condition by the crankshaft position pulses only during a fixed time interval following each cam shaft position pulse, in order to ensure stable operation when operating at very low engine speeds.

What is claimed is: 
     
       1. An ignition apparatus for an internal combustion engine having a crankshaft and a camshaft coupled to said crankshaft to be rotated thereby, comprising: crankshaft position signal generating means for detecting that said crankshaft has rotated to a predetermined angular position and for generating crankshaft position signals in response to said detection;   camshaft position signal generating means for detecting that said camshaft has rotated to a predetermined angular position and for generating camshaft position signals in response to said detection;   command signal generating means coupled to receive said crankshaft position signals, for generating ignition command signals in response to said crankshaft position signals;   ignition circuit means for generating a high ignition voltage in response to said ignition command signals;   enabling signal generating circuit means coupled to control said ignition circuit means, and coupled to receive said crankshaft position signals and said camshaft position signals, and adapted to be set to a first operating condition in response to said camshaft position signals whereby generation of said high ignition voltage by said ignition circuit means is enabled, and to be reset to a second operating condition in response to said crankshaft position signals whereby said generation of said high ignition voltage by said ignition circuit means is inhibited, and;   timer control circuit means adapted to control the transfer of said crankshaft position signals to said enabling signal generating circuit means, said timer control circuit means being responsive to said crankshaft position signals for enabling resetting of said enabling signal generating circuit means to said second operating state by said crankshaft position signals only during a time interval of fixed duration following each of said crankshaft position signals.   
     
     
       2. An ignition apparatus according to claim 1, and further comprising means for generating a signal when starting of said internal combustion engine is initiated, and for applying said signal to said enabling signal generating circuit means such as to establish said second operating condition of said enabling signal generating circuit means in which said high ignition voltage generation is inhibited. 
     
     
       3. An ignition apparatus according to claim 1, in which said enabling signal generating circuit means comprise a flip-flop which is coupled to be set and reset by said camshaft position signals and said crankshaft position signals respectively. 
     
     
       4. An ignition apparatus according to claim 1, in which said timer control circuit means comprise a capacitor, a source of a charging current for said capacitor, a circuit for discharging said capacitor in response to each of said camshaft position signals, and comparator circuit means for detecting when a voltage across said capacitor is below a predetermined threshold voltage level as a result of said discharging and for enabling transfer of said crankshaft position signals to said enabling signal generating circuit means only while said capacitor voltage is below said threshold level.